The application relates to resource allocation in a wireless system.
Discrete Fourier transform spread orthogonal frequency division multiple access (DFT-S-OFDMA) has emerged as the preferred uplink air interface for the next generation cellular systems such as the 3GPP LTE. DFT-S-OFDMA is essentially a modified form of OFDMA where users transmit their data on multiple subcarriers (frequencies) such that any two users are allocated non-overlapping sets of subcarriers. The key difference from OFDMA is that each user spreads its (coded) modulated information symbols using a DFT matrix and the spread (precoded) symbols are then mapped to its allocated subcarriers. The main advantage of this spreading operation is that with a proper mapping, it can result in considerably lower peak-to-average-power ratio (PAPR) compared to the classical OFDMA technique. The ideal sub carrier mapping in DFT-S-OFDMA for each user, which in fact results in the same PAPR as a single carrier signal, is an interleaved mapping where the subcarriers occupied by the user are equidistant from each other and span the whole system bandwidth. Unfortunately such a mapping precludes an important advantage of an OFDMA system which is frequency dependent scheduling gain. Thus, to balance the conflicting requirements of low PAPR and high scheduling gain, the DFT-S-OFDMA scheme employs localized mapping, where each user is assigned a set of (localized) contiguous subcarriers, henceforth referred to as a frequency chunk, on which it sees favorable channel conditions.